A 14-year-old boy in White Oak is being held at the Montgomery County Detention Center on charges he killed his 7-month-old sister Friday.

Johnathan Aguiluc of the 11600 block of Lockwood Drive has been charged as an adult with first-degree murder. He is scheduled to have his bond review at 1 p.m. today.

Members of the Montgomery County Fire and Rescue Service arrived at the boy’s apartment Friday morning and found Larissa Yanes unresponsive, according to a police report from the Montgomery County Police Department.

They contacted the police around 6:26 a.m. and officers were dispatched to assist them. The rescue team transported Larissa to Holy Cross Hospital in Silver Spring, where she died from her injuries at about 6:54 a.m., before police could arrive.

While preliminary investigation revealed that injuries found on the girl’s body at the time of death were not self-inflicted, Aguiluc admitted to beating Larissa in later interviews, according to the report.

Police learned that Aguiluc’s mother, Gloria Yanes, had left him to watch Larissa on Thursday when she went to work at 10:30 p.m. Aguiluc admitted in an interview with the detectives to beating Larissa and then covering her mouth and nose area with his hands when she started crying. The boy said he did this until Larissa stopped crying and then placed her in her car seat, which was in the apartment.

When the mother Yanes returned home at 5:30 a.m. Friday, she thought Larissa was sleeping and did not attempt waking her until around 6 a.m. so she could feed her. Yanes discovered Larissa was unresponsive.

Aguiluc was sent to the Montgomery County Detention Center in Rockville, where he was being held without bail. No one answered the door at a residence listed under Yanes’ name.

Aguiluc is an 8th-grader at Key Middle School in Silver Spring, according to Montgomery County schools spokesman Dana Tofig.